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(No Model.)

W. H. KNIGHT.

TELEPHONE EXCHANGE SYSTEM.

Patented July Z2, 1884.

IIIIIHI Illllxll] IIJIIIH INVENTOR.

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UNiTED STATES WALTER H. KNIGHT,

PATENT OFFICE..

oE NEW YoE'K, N. Y.

SPECIFICATION forming part of Letters Patent No. 302,344, dated July 22, 1884.

y Applicalionllled December 15, 1883, (No model.)

new and useful Improvements in Telephone-- Exchange Systems, which are illustrated in y Figures l and 2 of the accompanying drawings. l

My invention relates to switchboards for double lines.

In Fig. l of the drawings, A, B, C, and D represent subscribers stations, each having a double non-induction line, the two branches being equally distant from any other line, running to the central-office switch-board, and connected to the vertical strips l 12 2, &c. One end of every double line is normally plugged or otherwise connected to a common conductor, as shown by the cross at the junction of` bar K with strips l 2, &c. The other ends lare left free to be connected to any of the cross-bars b b2 b3, te., at will.

They preferably terminate in conductors passing through annunciators N, and then passing on to bar K. As the one set of ends are all connected, it is apparent that the free ends may be treated like the ordinary single lines running to the switcheboards now in use, and connected with one another in the manner now employed for single lines. Thus to connect subscribers A and C, their free ends l and 3 are plugged to a cross-bar, b', as indicated by the crosses. A and 0 are now connected through lines l and 3 and intermediate bar b, while they are also permanently connected by lines l and 3 and intermediate bar K. They are therefore on a complete metallic circuit, both lines of which pass from the subscriber to the central office and out to the second subscriber. done in the ordinary manner. When it is desired to connect a subscriber `having a single line, as E, with one having a double line, the single-line strip 5 is plugged to the barl, and the free end of adouble line, as B, is plugged to the same bar. It is necessary in this case that K have a ground-connection at Y, which will not interfere with its function as a common connector for double lines. The circuit is then from ground at subscriber E to strip 5, to b, to strip 2, to B, and back to central oflice by line 2, to bar K, to ground.

Calling is being equally distant from any external line.

D is a group of trunk-lines running to a second exchange, and also provided with a common return-wire. The common returns are all normally plugged to a common conductor, K, while the direct lines are left free for individual connections. Any two subscribers in the same group can be connected 'by simply plugging their lines to the same bar, as 2 and 3 A to bar r. Subscribers LLA' and 2 B are shown plugged to bar S. Subscriber 3 B and trunk-line 2D are plugged to bar t. At the second exchange trunk-line 2 is plugged to subscriber 3 A, their common returns being connected, so that 3 A at second exchange and 3B at first exchange are in communication. Subscriber 4 C is connected to single line subscriber E. It will thus be seen that any desired connection can be made, as with the presentswitch-boards, and yet the doubleline system completely preserved. In Fig. 2 the trunk-lines can come to cross-bars, as do lines L, if desired. It is not necessary that the return-lines should be strips with a place on the switch-board. They may be connected in any place and way at the central oilice.

I do not lay claim to some of the details shown in Fig. 2, nor to the method of trunkline connection.

What I claim herein isl. Twoor more double anti-inductive circuits, each having its two ends terminating in a central office, and having one of said ends there connected normally to a common conductor, in combination with devices for connecting together the other ends of the circuits at will, said common conductor and said connecting devices both forming parts of the conversing-circuit.

2. In combination, a switch-board, double anti-inductive circuits between'switch-board and subscribers', one end of each subscribers circuit normally connected to a common conductor at the switch-board, and means for con- ICO necting the other ends at will, so as to form a complete metallic circuit between subscribers,

including said common conductor.

3. Two subscribers circuits terminating in a central office and means at said office of connecting them, the outer terminals of said circuits being connected for conversation by an iuductivelyneutralizing conductor permanently continuous7 extending back through said central office.

4. rlhe combination of two or more subscribers lines connected to a common switch-board, cach line being accompanied throughout by its return-line, and said return-lines being permanently connected together at the central office.

5. The combination of two or more subscribers lines provided with annuneiators and parallel return-lines therefor normally connected to a common conductor at the central office.

6. The combination of a subscribers single line grounded at its extremity and a subscribers double anti-inductive line having one end permanently grounded at the central office.

7. The combination of a series of tWo or more groups of subscribers lines, each group being provided with a common return-line for neutralizing induction, the common returnlines being normally connected to a common conductor at the central office, and the individual lines being free for desired connections.

8. The combination of a subscribers line terminating at the central office, a return-line therefor, the direct and return being equally distant from any other line, and the return being permanently connected to a common conductor at the central ofiice.

W'ALTER H. KNIG HT.

Vitnesses:

ALBERT ELYNCH, W. E. DONNELLY. 

